Sewing machines capable of free motion quilting in addition to utility sewing have been provided conventionally. In utility sewing, the sewing machine executes a sewing operation while feeding a workpiece cloth by longitudinally moving a feed dog provided on a bed. In free motion quilting, the sewing machine lifts the presser bar having a presser foot mounted thereto and maintains the lifted state where the presser foot is spaced from the workpiece cloth by a predetermined small distance. Thus, the user is allowed to manually move the workpiece cloth placed on the upper surface of the bed freely.
A sewing machine capable of embroidery sewing disclosed in JP 2006-20757 A (patent document 1) is provided with a vertical movement mechanism that vertically moves the presser bar having a presser foot mounted thereto by a presser-bar driving step motor. The vertical movement mechanism is controlled by a control unit so as to maintain a predetermined small distance between the presser foot and the workpiece cloth during an embroidery sewing operation.
However, the sewing machine capable of embroidery sewing described in patent document 1 maintains the predetermined small spacing of the presser foot from the workpiece cloth not only during an embroidery sewing operation but also while the sewing operation is stopped. Thus, when the sewing operation is tentatively stopped during execution of free motion quilting, unintended user contact with the workpiece cloth causes displacement of the workpiece cloth. Also, a displacement of workpiece cloth may occur by the weight of the workpiece cloth itself when sewing a large workpiece cloth. The displacement of workpiece cloth causes displacement in sewing position when restarting the sewing operation, that is, the displacement in the position where the stitches are sewn.
In order to prevent sewing position displacement of the workpiece cloth when restarting the sewing operation, the sewing needle may be moved downward to a needle lowered position and anchor the sewing needle through the workpiece cloth when the sewing operation is tentatively stopped. However, in case of sewing large workpiece cloth, since the ends of the workpiece are pulled downward by its own weight, the sewing needle penetrating the workpiece cloth may be bent or a needle drop hole of the workpiece cloth may be pulled open and damage the workpiece cloth.
Also, when tentatively stopping the sewing operation, the presser foot may be lowered by manual operation of the presser foot lifting lever so that the workpiece cloth may be pressed by the lowered presser foot. However, manually lowering the presser foot upon every instance of stopping the sewing operation is cumbersome for the user and reduces work efficiency.
Further, in case of employing a generally used quilt presser that press the workpiece cloth intermittently; the workpiece cloth cannot be pressed by the presser foot when the sewing needle is placed in a needle raised position. Thus, as described earlier, the workpiece cloth may be displaced when the sewing operation is tentatively stopped in which case the position of the stitches sewn on the workpiece cloth when restarting the sewing operation is displaced.